Fructose-1, 6 diphosphate is anaerobically metabolized to yield 4 mol of ATP. The vaso-occlusive crises of sickle cell disease are characterized by tissue ischemia due to hypoxemia. Hypoxemia promotes the change from flexible erythrocytes to rigid sickle cells and aggravates tissue ischemia. Providing energy by increasing intracellular ATP may prevent sickling and shorten crises. A dose escalation study will be performed in three stages. This pilot study should establish the tolerability of FDP and the efficacy and safety of this agent.